<!DOCTYPE html>
<html lang="en"  xmlns:th="https://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title th:text="#{app.welcome.title}"></title>
    <style>
        body,html{
            width: 100%;
            height: 100%;
            display: flex;
            justify-content: center;
            align-items: center;
        }
    </style>
</head>

<body contenteditable="true">
<span th:if="${session.lang} eq 'en'"
      th:text="#{app.welcome(${#authentication.principal.username})}"></span>
<span th:unless="${session.lang} eq 'en'"
      th:text="#{app.welcome(${#authentication.principal.niceName})}"></span>
</body>
</html>